


Mating Habits

by Chiisanafukuro (makuro)



Series: Galra Habits (Galra Shiro AU) [2]
Category: Voltron: Legendary Defender
Genre: Anal Sex, Creampie, Galra anatomy, Galra!Shiro AU, Knotting, M/M, PWP, Porn, keith gets wrecked by his big boyfriend, semi/echoes of ABO?
Language: English
Status: Completed
Published: 2018-12-23
Updated: 2018-12-23
Packaged: 2019-09-25 05:53:19
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,923
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/17115662
Author URL: https://archiveofourown.org/users/makuro/pseuds/Chiisanafukuro
Summary: Keith finally gets fucked by his boyfriend





	Mating Habits

**Author's Note:**

> So [@Jotakorium](https://twitter.com/Jotakorium) 's Galra!Shiro AU with the, ah size kink, well. That's a... that's a thing right there. 
> 
> This was written in an hour and I didn't check it over because omfg

“Hah…ha…. Ahnnggg, yeah, yeah, _shit_.”

Keith bottomed out, his ass finally sitting back against Shiro’s thighs. He could feel his mate trembling behind him, trying to keep still while his length was finally sheathed deep in Keith. The bulge in his stomach was at once erotic and disturbing. He could feel Shiro up in his guts, but Galra anatomy was a fascinating and accommodating thing.

When they had first started to court Krolia had given Keith his long overdue Galran birds and bees talk. The Black Paladin, versed in literally every situation on the planet, had not been ready for his mother to explain that his body would stretch and expand for lovers, especially in rut or heat, and that he needed to get shots.

“Why?” Keith had asked.

“You’re both young and virile, we don’t need you getting knocked up right now Keith.” She’d sounded exasperated. The earth raised Keith had blanched and nearly fainted.

While, as far as Galra went, his mother’s clan was small, it was also apparently the most physically versatile. Hence his ability to shift form a bit when stressed, or furious, or having his boyfriend’s cock rummage around in his ribcage _fucking hell_ how did this feel so good.

“S’your cunt,” Shiro slurred, rocking a little inside of Keith. “It’s built for this.”

Keith moaned and wiggled on the shaft he was speared open on. No wonder his father never took him to the doctors.

Shiro’s huge hands gently wrapped around Keith’s thighs and began to lift him in time with the shallow thrusts and long, swiveling grinds of Shiro’s massive dick. The squelching noise from all the lube in Keith filled the room. The thighs he was sitting on where sticky with it where it was slowly trickling back out of his hole.

Shiro mouthed over his shoulder, teeth lightly scraping, and Keith’s cock twitched, precome blurting out of the tip. He already needed to come and Shiro had just gotten all the way in.

They’d worked up to it. Even with reassurances from Shiro and, embarrassingly, Ulaz, he didn’t want any chance of something going wrong. More for Shiro’s sake than his own. Shiro was always afraid of hurting Keith on accident. So they had gone slowly with the prep. Fingers, toys, and finally today when Keith wore a plug through his morning routine and briefings, only to take there rest of the day off with Shiro.

He hand’t told his lover what he’d done, instead Shiro ripping off his clothes and finding the plug nested deep in Keith’s ass, thick and wide and covered in globs of lube. Wriggling it out had takes some effort, but by the end Keith was a mess. His ass was gaping, his cock was throbbing, and now he was finally, _finally,_ sitting on Shiro’s cock.

He felt it twitch inside of him when his insides clenched down on it. “Fuck me,” Keith breathed, his whole body shaking with effort and need. “Shiro, please.”

Shiro hummed and continued his slow pace. Rocking Keith on his cock like he was trying to lull him to sleep, not stuff him with seed.

So when sharp claws thumbed over taut, sensitive nipples, Keith was totally taken aback by his orgasm. It ripped through him like lightening, come spurting out of him and coating his lap and Shiro’s.

“That’s it baby,” Shiro cooed. His index finger stretched out and traced lightly along the vein on Keith’s dick. Which was still hard, and aching, even with come dribbling out of the tip. “Let’s get you going.”

“Wha… going? What? Nng, fuck, Shiro, what’s happening?” He was coming down off of his high, but not enough, and he was _still painfully hard._

Shiro pulled away a bit and let Keith hang there on his cock, the size of it keeping him up as much as Shiro’s grip on him. “Did… they not tell you about this part?”

“Hng, no.” Keith wanted to cry. He wanted to come, again, moments after unloading. He felt dizzy and inside of him Shiro’s cock was grinding against places he didn’t know could feel _so good_.

“When, _ah_ , sometimes when mating we can,” Shiro was panting, clearing straining to not fuck into Keith before he got done explaining this. “Our hormones go into overdrive, almost like a heat, or a rut, if you will. Leftover mating instincts.”

“What… oh _god_ , what does that mean?”

Shiro tilted forward, his finger still running up and down Keith’s weeping cock. “We won’t be… fully satisfied until I knot.”

His cock shifted inside and Keith wailed in pleasure. “Oh fuck fuck fuck FUCK! Shiro!” He came again, weakly, but still with stars behind his eyes and fire down his skin. His dick never waned through it, still red and leaking. Keith’s head lolled back onto Shiro’s shoulder.

“Oh god,” he whined. “How long?”

“Un, I don’t,” Shiro thrust up shallowly and punched all of the air out of Keith’s lungs. “I don’t know. Here, baby, let me…” He put a hand over Keith’s chest, his thumb tracing over a nipple. Keith keened but the sound ended up muffled in the bedding as Shiro tipped them forward, Keith on his belly and Shiro mounting him from behind.

“Is that better?” Shiro asked. He might not have meant to punctuate that with sinking in deeper, but it’s what happened.

“Hng,” Keith responded. He got his legs under him and shifted his ass back and forth, fucking himself on Shiro’s dick.

He was engulfed by Shiro, his body, his scent, his cock riding deep inside. It was easier to thrust for him like this and he wasn’t holding back now. Keith’s body was rocked as Shiro plundered inside with some gusto now. He was still being slow, careful with his mate, but he was taking pleasure for himself now that Keith was adjusted.

And twice orgasmed.

His cock was trapped between the bed and his stomach, even that little bit of friction doing it for him with the massive Galran equipment lodged in his abdomen.

Shiro reached under him to palm at Keith’s thighs again, grasping them and hauling them up for a better angle.

Keith screamed when Shiro pulled almost all the way out and punched back in, another orgasm ripping through him. Thick ropes of come spattered between him and the mattress.

He slumped over again, this time though it did feel like he was just hanging off of Shiro’s cock, Shiro poised above him like he was.

“M’still hard,” Keith cried. He did really feel like crying. Each time he’d come it was almost blackout good, but still not enough.

Above him Shiro growled, a true deep growl. Keith’s own body vibrated with it since Shiro was still fucking into him.

“Shiro, _please_.” He wasn’t sure what he was asking, not really, just that he needed something from the man plundering him, as if it wasn’t already enough.

Shiro growled again and punched his cock into Keith, hard, and merciless. He pulled out almost all the way before slamming in again. And again. And again. When he met little resistance from Keith’s gaping, messy hole, he finally started to fuck Keith in earnest.

Keith was helpless to it anyway. All he could do was sob and babble while he took Shiro’s cock. It felt so good now, the stretch and the awkward fullness replaced with what felt like a never ending orgasm. His body was vibrating it and his dick was just leaking come into a puddle on the bed. Keith’s soft insides were welcoming Shiro’s length. He kept it together enough to push his ass back onto Shiro’s cock on the odd thrust. Each time he did he was rewarded with his entire body being vibrated by Shiro’s rumblings.

“That’s it baby, take it. Take my cock. Take your pleasure from it. You’re doing so well little love.”

Keith lost track of everything but the giant cock in his gut and his own unyielding pleasure. Shiro’s cybernetic arm snaked down to hold his poor dick at some point. Shiro made it vibrate on a relatively low setting, but even that had Keith screaming from oversensitivity and spurting over Shiro’s fingers.

The entire while Shiro as rumbling praises into Keith’s ear. “You’re doing so well, baby. Just a little more I’m almost there I promise.”

All Keith could do was whimper and take it.

Just when he thought he couldn’t endure more pleasure the based of Shiro’s cock caught on his abused rim. It did so with increasing pressure until Shiro was stuck inside, grinding Keith’s entire body into the bed.

“Wha is that?” Keith managed, the shock brining him out of his stupor a bit. His voice was cracking, words slurring over each other. Shiro managed to make out what he was asking though.

“Knot, its, umph, my knot. Fuck, Keith, you feel so good.” The base of him began to swell, locking Keith on his cock. Shiro moaned, low and deep.

Keith was so fucked out he didn’t feel it at first. The knot was there, stretching his rim to the limit, but the hot wet gush inside him didn’t register over the increased girth at first. Then, slowly, he became aware of his insides getting filled up with Shiro’s come.

Above him Shiro was purring and let the vibrations of his hand max out.

Keith howled as his balls emptied for a last time onto the bed. It felt like he was going to come so hard his insides would be hallow. The oragasm wasn’t ended, ropes of come coating him while Shiro was still dumping his load inside. He could feel it squelching out from around Shiro’s cock, his insides not enough for the volume of come flooding him.

He passed out like that, sticky, still coming, with Shiro’s seed leaking out in rivulets down his thighs.

 

How many moments had lasted between passing out and this Keith didn’t know. Shiro’s knot though had gone down and he was easing out of Keith. As he did come was gushing out of Keith in waves, ruining the bed completely. He was laying in a puddle of his own spend, stomach wet and itchy with it in the few places that it had dried.

When Shiro’s head, still fat when semi-flaccid, popped out from Keith’s rim a river of come poured out. Keith could see himself, his ass abused and red, hole winking around air and pulses of come. Shiro’s thick cock resting and spent on his thigh.

He didn’t think he had any come left in his body but the thought of of what he must look like had it shooting off again and Keith passing back out.

 

When Keith came to the second time he was in warm water, cradled against Shiro’s chest. His body felt like it had been pulled between two black holes.

“What the fuck happened?” He croaked.

Shirp rubbed a soothing hand over his stomach. “We uh… well the good news is we’re very compatible partners. Triggering a mating cycle like that is pretty rare, babe.” His voice trailed and the unsaid other half of the news was hanging in the air.

 

He sunk down into the water more, letting it melt away some of the aches. “And the bad news?” Keith whimpered. He wasn’t sure he was going to be able to walk on his own any time soon.

“We may have to schedule vacation time for when you want me to fuck you.”


End file.
